The present invention generally relates to a gear-type fluid displacing machine and, more particularly, to external gear-type hydraulic pumps or motors and, still more particularly, to improvements in the operation of such hydraulic machines.
During the operation of presently known gear-type pumps, the finite number of component parts of such machines causes non-uniform delivery of fluid to be pumped to a user. The torque characteristic of such machines also varies widely between maximum and minimum values. Such non-uniform operation is highly unsatisfactory for most commercial applications.
Moreover, during operation of such gear-type machines, the rotating gears are subjected to forces which urge the gears to move relative to each other due to an unequal distribution of pressure which exists in the region about the gears. Such forces have a force component which urges the gears, and concomitantly the bearing members which journal the gears, towards each other. Moreover, such forces have a force component which urges the gears against the inner circumferential wall of the housing chamber in which the gears are mounted.
Such forces are highly undesirable because they generate fluctuations in the rate and quantity of the fluid to be displaced in the machine, thereby decreasing the efficiency of the operation of the machine. Such fluctuations also generate chatter and prevent quiet, smooth-running operation.